He said the beefed-up program of targeted pre-games and pre-competition testing — as well as the storage of doping samples for 10 years — was working as a strong deterrent.

"It's expected that people don't cheat and those who do are not here," Ljungqvist said, noting that only one positive case was recorded at the 2010 Vancouver Games.

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"It shows that the program is pretty efficient and serves as a deterrent," he said. "I hope it will stay that way throughout the games."

Through Friday night, Sochi organizers had conducted 1,799 drug tests, more than half of the planned total of 2,453 for the entire games. Of those carried out so far, 1,140 were pre-competition tests and 659 standard post-competition controls.

Ljungqvist was asked whether the reason there have been few positive tests at Winter Games is that cheaters are ahead of the testers.

"I put my money on our scientists," he said. "They are probably smarter than those around the athletes."

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The IOC is focusing its efforts on unannounced tests away from the competitions, considered the most effective way of nabbing any cheaters. Athletes and sports considered most at risk are targeted for testing, based on intelligence provided by authorities, athletes and previous test results.

The majority of tests are conducted in strength and endurance sports, notably cross-country skiing and biathlon, events where the use of EPO and other blood-boosting drugs can aid stamina.

The IOC also stores Olympic doping samples for retesting years later when new methods become available. The storage period has been extended from eight to 10 years under the next World Anti-Doping Code.

"The message to the athletes is that if you cheat, if you take drugs, if we don't find you now, we may find you later and we will certainly find you sooner or later," Ljungqvist said.

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The IOC recently retested 350 samples from the 2006 Turin Winter Games, but has not released the findings.

The Estonian Olympic Committee said last week that retired cross-country ski champion Kristina Smigun-Vahi was under investigation by the IOC for a positive sample from Turin.

Smigun-Vahi, who won two gold medals in Turin, in the 10K classical race and the 15K skiathlon, denied ever using banned substances.

Ljungqvist declined to comment on the Estonian announcement, saying the Turin results would only be announced sometime after the Sochi Games.

Ljungqvist urged other national and international bodies to follow suit and store doping samples for retroactive testing.

"It's an important deterrent — that the athletes know if I get away with it today, they are steadily for a 10-year period under threat of being identified," he said.

On other issues, IOC medical director Dr. Richard Budgett said athletes in Sochi can even be tested at the medals plaza in the Olympic Park, if they were unable to give a full sample earlier at the mountain venues.

"In addition to that, there is a van which follows the athletes down so if they really, really need to go on that short journey down from the mountain that can be dealt with as well," he said.

Budgett also confirmed that NHL players have been under Olympic drug-testing rules applied by the international ice hockey federation since Oct. 1. Since Jan. 31, the players have come under the IOC's games-time program, including testing for HGH, just like all other athletes.